SIZE DIMORPHISM, JUVENAL PLUMAGE, AND TIMING OF BREEDING OF THE HYACINTH VISORBEARER (AUGASTES SCUTATUS)

摘要

The Hyacinth Visorbearer (Augastes scutatus) is a poorly known hummingbird endemic to the Cadeia do Espinhaco in southeastern Brazil and is classified as near threatened with global extinction. We verified size dimorphism of males and females, describe the plumage patterns of juveniles, and detail the reproductive period of this species in Serra do Cipo National Park within the municipality of Morro do Pilar in the State of Minas Gerais, Brazil during August 2007 to July 2009. Adult males were significantly larger than adult females in all measurements assessed. Variables that best differentiate males and females are body mass, total body length, occipital width, bill length, and wing chord. We demonstrated that it may be possible to assign gender of the majority of young of this species, based primarily on the color of the side of the neck and the tract of feathers that circles the visor. There is some indication of a greater concentration of reproductive effort during the dry season, when more juveniles and active nests were recorded. However, we captured fledged young in January, February, and March supporting a breeding period throughout the year for the Hyacinth Visorbearer. This suggests rainfall in the region is the most influential factor in timing of breeding of this species.